It seems to me that people are actually missing Vita's issue, at least, depending on what your expectations are. See, part of the problem is people see Vita as directly competing with the 3DS - and it is, there's no doubt about that, but it also has narrowed itself in the way it was built, with it's price, and the technology in the system into a higher end, niche market. There is nothing wrong with being a higher end system, the problem is Sony is still stuck with the same mentality gamers had during the Genesis/SNES days, where the thing that matters is competing with the other guy, with finding your nemesis and whipping out a ruler.
The reality though is it's not that clear cut. Sony is trying to appease their userbase and the media by appearing to compete with Nintendo while targeting wholly different markets. The Vita will never catch the 3DS for the same reason the PSP was never going to beat the DS. High end sounds great, and it will be popular with the hardcore high end consumers, the specialists, the tech oriented hardcores who want the "coolest" thing out there. But it can't compete with a competitively priced mainstream system with Nintendo's moniker and without the baggage a Nintendo console often attracts.
There is another point though, even aside from the demographic challenge. Yes the PSV is a nice hardware upgrade from the PSP but what does it do so much substantially different from the PSP that it is going to attract the audience it would need to "catch" the 3DS or even significantly take a bite out of it's sales? The PSV is a "Safe" system. It's sleek, it's beautiful, it's familiar... but if that's all it is it's not really a "game changer." Powerful system merely because they are more powerful have never been decisive in a battle between system. Of course content matters, but so does having a unique "hook" that draws consumers in by in some way showing you're being innovative. The Wii was perceived that way with consumers because motion gaming hadn't really been done on that scale before. The PSV if it was to seriously compete with the 3DS would have needed some sort of hook that differentiated it from the 3DS. I mean, heck, the DS itself was a different approach to gaming than GameBoy with a wholly revamped design meant to refresh the brand. I think that "newness" contributed to the system's success.